Mobile telephone communications by vehicular and handy phones have improved in quality and have greatly increased in number these days, as they are more and more widely used in daily life as well as for business.
These mobile telephone communications by vehicular, handy, portable or mobile phones are based on the premise that the phones are moving at all times. When the terminal machine or mobile phone is switched on, or starts its transmission, or moves from one base station to another (each base station having a function that allows radio communication to be exchanged between the mobile phone and itself), a system for enabling the current location of the mobile phone to be registered or updated in the database is employed in the communication network. In the location register system for mobile communications by vehicular and handy phones, radio-wave propagation or base station areas Ea, Eb, - - - (each having a radius of about 4-5 km and including each of the base stations A, B, - - - ) come together to form each of the large calling areas E (each having a radius of about 10 km), as shown in FIG. 1, and the location register of each phone is made in every calling area E. In short, when the mobile phone moves from one calling area to another, it transmits the information that it has moved to a new calling area, and its new location is thus updated. In the conventional mobile communications by vehicular and handy phones, therefore, the location of each mobile phone can be registered in every calling area (being quite a large area, equal to that of a prefecture in the Japanese administrative system).
Mobile communications by vehicular and handy phones can even be made when the mobile phones are moving at high speed, and the area over which communication can be made is quite large. They are therefore extremely advantageous for businesses. Their basic and communication fees, however, are still quite high so that they cannot penetrate yet into domestic and small business markets.
The personal handy phone system (PHS) has now been developed to solve this problem. The PHS results from the consideration that cordless phones now used in homes can be made usable outdoors. Communication with the PHS is not possible when its mobile phone is moving at high speed, but it is possible at low speeds, like when the phone user is walking, for example. Compared with the conventional mobile communications by vehicular and handy phones, therefore, its function has some limitations, but if its basic and communication fees could be reduced, it is expected that it could be used more widely and easily in homes and other places.
When a mobile communication system incorporating this PHS is used, it can be expected in the future that the mobile phones of the PHS will have a function which allows their locations to be registered in a far smaller area. In addition, it can also be expected that more accurate location information showing where PHS users are currently located will be obtainable in homes, and when the system has this function to accurately detect and to register locations, elderly people and young boys and girls can safely leave their homes at night for some activity, taking with them a mobile phone of this system. It can be therefore expected that this system will become extremely useful in business as well as in daily life.
However, the location searching or detecting system of the PHS has not yet been embodied. In the conventional mobile communications by vehicular and handy phones, the location of each phone can be registered. The calling area, however, in which the location register is made possible is quite large, equal to that of a prefecture in the Japanese Administrative system, so this system cannot be used, as it is, for the PHS, from the viewpoints of the location register area and the basic and communication fees. A system enabling the location of each phone to be registered in a far smaller area is therefore required for the PHS.
An object of the present invention is therefore to provide a location searching system for the PHS, having a function to allow the location of each mobile phone to be registered in a far smaller area, and to be capable of reading this location information which is registered and restricted to a smaller area, and thus passing this location information to the home, when the mobile phone user""s home asks the PHS where the end user is.
According to the present invention, location data transmitted from mobile phones in every area Ea, Eb, or - - - (having a radius of about 100 m) to each of base stations A, B, - - - can be registered in a common database through a PHS exchanger.
When a mobile phone is in the area Ea of the base station A, for example, it transmits its location information in response to a signal transmitted from the base station A, the signal having a frequency characteristic of the station A, and this location information is then registered in the common database. When it moves from the area Ea of the base station A into the one Eb of the base station B, which is adjacent to the area Ea, it again transmits its location information in response to a signal transmitted from the base station B, said signal having a frequency characteristic of the station B, and this location information showing that it is now in the area Eb of the base station B is registered in the common database. Therefore, every time the mobile phone moves from one base station area into another, therefore, its location information is updated in the common database. Radio propagation ranges in the areas of two adjacent base stations (such as stations A and B, for example) usually overlap each other. In this case, however, its location information is registered to be in that area from where a stronger radio signal is transmitted. In order to detect which base station area it is in, specific data may be allocated to each base station by changing its carrier frequency a little or by applying frequency or phase modulation to the radio signal transmitted.
In the conventional mobile communications by yehicular and handy phones, it is a fundamental communication function that the location of a mobile phone is registered in the common database when the phone is switched on. In this case, however, this location information is registered every calling area (being a collection of several base station areas, as described above, and which corresponds to an area denoted as a xe2x80x9cchomexe2x80x9d in the address format of the Japanese administrative system). Namely, when the mobile phone is switched on, the location is registered of that calling area in which the phone is currently located, and when it moves from one calling area to another, the location is registered of this new calling area. In short, the location information in the common database is usually updated for every calling area.
According to the present invention, however, the mobile phone allows its location to be registered at every base station area, as described above. In short, its location can be updated every time it moves from one base station area to another (from the base station A to the base station B, for example).
When the mobile phone user leaves his home and is currently in the area Ea of the base station A, the mobile phone transmits his location information, which shows that he is now in the area Ea of the base station A, in response to a signal which is transmitted from the base station A which has a frequency characteristic of the station A, and his location is registered in the common database. When he moves from the station A into the area Eb of the station B, the mobile phone transmits his location information, which shows that he is now in the area Eb of the station B, in response to a signal which is transmitted from the base station B which has a frequency characteristic of the station B. His location information which has been registered in the common database is thus updated with his new location information showing that he is currently in the area Eb of the base station B. The latest location information can be registered in this manner in the common database for every base station.
When his business company or his home ask where he is currently, access is made to the common database and the current location information of the mobile phone is read, using the subscriber number of his phone as a key, and this information is sent to his business company or to his home. When a software program is prepared in such a way that when he is in the area Ea of the base station A, that area can be specified to a lot number xe2x80x9cor No. 1, 1-chomexe2x80x9d using the address format of the Japanese administrative system, and that when he is in the area Eb of the base station B, that area can be specified to a lot number (or No. 2, 1-chome), then more precise location information can be sent to his business company or to his home. In short, the current location of his mobile phone can be specified to a spot denoted as a lot number in the address format. Thus, the present invention can specify a location of the mobile phone within an extremely small area.